With the growth of combinatorial methodologies has come a need for rapid, high throughput, evaluation of combinatorially formed materials. Rapid screening methods that require only small quantities of material are increasingly in demand. Recently, Cong, P.; Doollen, R. D.; Fan Q.; Gianquinta, D. M.; Guan, G.; McFarland, E. W.; Poojary, D. M.; Self, K.; Turner, H. W.; Weinberg, W. H. Agnew Chem. Int. Ed. 1999, 38, 4, 484 reported a quadrupole mass spectrometer screening method for heterogeneous catalysis libraries in a sequential fashion. In Cong et al., each catalyst site of the library of catalysts was sequentially heated to a desired reaction temperature by a carbon dioxide laser. Reactant gases were then transported to the catalyst site through the annular section of a double concentric probe in a stagnation-flow manner.
A similar quadrupole mass spectrometer based screening technique was also reported in Orschel, M.; Klein, J.; Schmidt, H-W.; Maier, W. F.; Agnew Chem, Int, Ed. 1999, 38, 18, 2791, where the library consisted of an open structure where catalyst powders, prepared by the sol gel method, were placed in a spatially addressable configuration on a heated substrate. Screening was achieved by sequentially flowing a feed gas onto the surface of a catalyst spot through a capillary feed line and by withdrawing the products through another capillary line.
WO 99/19724 describes a method for rapid screening for activities and selectivities of catalysts by contacting potential catalysts at the test sites with a reactant stream to form product plumes. The product plumes were screened by passing a radiation beam to promote the formation of specified photoions and photoelectrons which are detected by microelectrode collection in situ in proximity to the respective test site.
WO 00/29844 describes a method of screening for activities and selectivities of catalyst libraries by contacting the catalysts at the test sites with a reactant stream to form product plumes. The product plumes are screened by translating a sample probe and/or the library to sample the product plumes and to conduct the plumes to a mass spectrometer where they are analyzed. One drawback to each of the above technologies is the extensive requirement for moving parts within the apparatus. Besides adding to the cost of the equipment, moving parts require a greater degree of maintenance, become a likely cause for mechanical failure, and, most importantly, may limit the speed with which the apparatus may be used to screen materials.
Still others have tried methods for screening libraries of materials using mass spectrometers; see U.S. Pat. Nos. 5,959,297 B1 and 6,248,540 B1 where one embodiment shows a small volume created next to a library and filled with reactant gas. Selective IR heating of a thin substrate activates a library element of interest resulting in products which flow to a detector. U.S. Pat. Nos. 5,959,297 B1 and 6,248,540 B1 also state that a flow-through geometry can be employed.
The present invention provides a rapid screening method and apparatus that requires no moving parts and permits easy relative determination of a variety of characteristics. The present invention is a heat activated selective membrane introduction cell and detector for high throughput screening of materials such as inorganic solids, adsorbents, and heterogeneous catalysts. Advantages of the present invention include separating the effluent using a semipermeable membrane prior to conducting the effluent to a detector and using an array support as a thermal barrier to protect the semipermeable membrane from thermal degradation.